1. Field of Invention
This invention relates to roll forming; a technique of progressively and continuously folding material by means of successive pairs of profiled rolls, the rolls in each pair being described as "bottom rolls and top rolls" respectively. The roll pairs are also known as stages, stands or passes. Rolls in the successive pairs have a different profile to effect differing degrees of folding of material passing between them. In use, material is fed into a roll forming machine at one end between the pairs of rolls, either as cut as sheets or in coil material, and is progressively folded by the successive pairs of rolls in a series of discrete steps to emerge at the other end of the machine formed about the feed axis. The rolls in the pairs may both form and drive the raw material through the machine. The material most commonly formed is steel, but non-ferrous metals and other materials are formed by this method.
2. Description of the Prior Art
A comprehensive background for the roll forming technique is provided by, for example, "Cold Forming", W. G. Kirkland, Iron and Steel Engineer, November, 1959 and "A Survey of Sheet Metal Cold Roll Forming", M. A. Wallis, British Steel Corporation Corporate Laboratories Paper Number MW/36/71.
A schematic illustration of such a conventional roll forming machine is shown in the accompanying FIG. 1. (The figure shows only a selection of roll pairs and the usual roll supports are omitted for the sake of clarity. In the machine, driven forming roll pairs are mounted so that each roll in a pair is rotatable about a generally horizontal axis. Adjacent roll pairs have slightly differing profile so as to effect correspondingly differing degrees of folding to material passing through the machine, from the roll pair 139 towards roll pair 140.
In addition to the driven forming roll pairs 139, 140, the machine may also include auxiliary rolls 141, which are normally undriven and often rotate about an axis arranged at an angle to the horizontal axis of the main driven rolls. Such auxiliary rolls allow access to parts of the material which are not accessible by the driven forming rolls. Also use of such auxiliary rolls may be advantageous in preventing scuffing of the raw material. Typically, the auxiliary rolls are more readily adjustable than the main driven rolls.
As previously discussed, on such known roll forming machines the profiles of the roll pairs mounted in the machine determine the formed shape of the product and thus the roll pair must be made specifically for a particular shape, size and thickness of product. Thus, adaptation of a machine to form a product of different shape, or size or to accommodate anything more than minor raw material thickness alteration requires a change of bottom and/or top rolls.
This is disadvantageous because a change or roll pairs may take many hours as the new set of roll pairs may require some setting. Additionally, the roll pairs are usually made from hardened alloy steel to high degrees of accuracy and each set is designed individually and may take some weeks to manufacture. As a result, many man hours of labor are required to make the average set of roll pairs.
The cost of a set of roll pairs means that the product to be produced will have to be made in high volume to justify both the initial roll pair cost and also the roll change and setting time.
In recent years a number of techniques have been employed in the attempt to improve machine versatility and production flexibility by seeking to reduce roll change and setting times. In essence these techniques enable a quick change from one predetermined machine section to another. For example, such techniques may involve the removal of a complete set of roll pairs, still mounted on their stands and shafts, known as a `raft` and the substitution of another complete raft. See, for example, the accompanying FIG. 2 in which the roll pairs are mounted on a base comprising a fixed part 145 and a removable part 146. Repositioning of part 146 on part 145 is typically assisted by way of pegs indicated generally at 147.
Such a `raft` method is usually used for producing wide panels where production runs are very high and the roll sets are large and more costly than average.
Also another variation is to mount individual roll pairs, their shafts and stand onto a plate. This assembly, known as a `cassette`, can be changed for another cassette. An example cassette assembly is illustrated in FIG. 3. Here again the roll pairs are mounted on a removable base part 148. This time the part 148 is divided into sections; one for each roll pair. Repositioning of the removable part 148 on fixed part 145 is again assisted by way of pegs 147.
There is also the method of having two sub-sets of roll pairs mounted on cantilevered or overhung shafts facing each other and which together make one forming set on two `heads`. The heads can be pivoted about a vertical axis and other roll sets brought into play if similar cantilevered roll sets are mounted on the horizontally opposing side of the heads. This is illustrated schematically in FIG. 4.
A further technique, similar in principle, mounts sets of top and bottom rolls on a type of carousel about a horizontal axis. A change of rolls is achieved by indexing the top and bottom carousel by a portion of one rotation. A second predetermined roll set then comes into play. This latter method usually has the disadvantage of not being able to drive the raw material at the same time as forming it. Other rolls must be provided to drive the material.
The techniques outlined above seek to avoid the removal of individual rolls in the roll pairs from shafts and subsequent fitting of others. They also rely on the rolls in the pairs being designed to take account of a pre-determined change from one product shape to another and therefore allow the machine to be adaptable for forming products within a limited range of shapes and sizes. Essentially, the aforementioned methods provide for quicker changes between pre-determined configurations.
Australian patent AU-B-26163/84, Applicant John Lysagne (Australia) Ltd. entitled "Roll-forming Machine", shows how axial movement may be accomplished and no device is shown now any movement at right angles to it may be carried out. Moreover, the removable roll segment is limited to being slideably mounted on the same shaft as a fixed roll segment. The pedestal axial movement provided then moves the pair of roll segments. The roll segment is therefore not truly independent.
The axial adjustment that is provided for the slideable roll segment is mounted on the shaft carrying the roll segment and is therefore not suitable for remote adjustment. The means of adjusting the slideable roll segment rotates with the roll shaft and cannot be connected to an adjuster nor can the machine be adjusted at this point while the roll rotates.
The pedestal movement is adjustable but not readily suitable to automatic adjustment since the pedestal once moved must be clamped by a second means. This is a mechanism that is only suited to manual adjustment involving clamping and unclamping between adjustment.
In UK Patent Application, GB 2188 859 A, date of filing Apr. 9, 1987, Applicant Hayes Engineering Ltd., there is no provision for roll movement up or downwards. The rolls are termed roll elements but in no way can they be segmented to the extent required for change in the formed profile that is not a series of pre-determined forms. The alterations that can be accomplished are limited to a variation in profile width and in the orientation of the profiles at each end. The example of forming shown is that described in our application under the term `air-bending`. This is where the variation in leg lengths up the formed angle are not controlled by any restraining part of a roll profile.
U.S. Pat. No. 4,117,702, Inventor Gene N. Foster, Assignee The Boeing Company, Seattle, dated Oct. 3, 1978, describes a pinch or pyramid forming machine and not a roll forming machine which has sequential pairs of rolls arranged along an axis. Its propose is to curve a pre-formed and straight profile into a curved profile.
The machine described shows how roll movement is to be carried out in a direction transverse to the rotation axis, i.e. towards the center of curvature of the formed product. No means is shown for moving the rolls in a direction parallel to the center of curvature of the formed product as would be necessary for true flexibility. The reference to rolls being able to move along one or more forming axes refers to rolls mounted on axes at an angle to one another.
A person familiar with the art of roll forming could not adapt this principle to the pairs of rolls required for roll forming of products from flat strip as is described in our application. The reason for this is the lack of a mechanism for moving roll segment in both x and y axes and for a mechanism that does this and allows the type of interlacing of roll segments needed that we show with the simultaneous possibility of providing drive to the formed product.
The manufacture of conventional roll pairs can be made more economical by splitting an individual roll up into pieces, allowing the roll to be dismantled and some of the pieces re-assembled and securely fixed together to provide a profiled roll having a different configuration by addition of other suitable pieces. Also as regards economy, it has recently become possible to assist the roll design process by specialized Computer Aided Design Software. This has enabled designer to produce drawings more quickly and manufacturers have been able to take advantage of the design data in electronic form. Economy of the method has, therefore, been improved, but not dramatically.
A final alternative is the so called "air-bending" method, which, for example, can be used to vary the leg lengths of channel shapes by leaving the ends of the legs unrestrained by `traps` (a face against which the end of the strip lies). Unfortunately, this method risks inaccurate leg lengths on the product where parts of the roll profile are not used to control material movement.
Despite the above work, the roll forming technique remains one in which, if product quality and dimensional accuracy are to be retained, individual roll pair shape or profile is fixed and to change this profile requires removal of top and/or bottom rolls from the shaft or rotation of a larger assembly. The present invention seeks to overcome at least some of the aforementioned disadvantages.